Those are the outer half of fairly standard Euro trailer windows - the Predom/Cadet doesn't need the fixed half as that is moulded into the fiberglass. You should have a seal attached to the body around the window opening, which it sounds like you're missing. It's just visible in this photo of a modern Predom.
Incidentally, those windows are now normally made in Europe with two layers of plastic to give double-glazed windows. I've not seen this on a Predom/Cadet, but they may be made that way by now.
Since these trailer sare still being made, the simplest solution might be to buy an awning intended to go on one: English awnings (£425 is about $800), Dutch awnings.
Thanks, Andrew, for the link. I will be in London in May but I don't think either the window or the awning
will fit into my suitcase!
There is a lot of old caulking around the left top corner of the front window and it looks like the window corner has been bent and the caulk was the fix. When I strip everything out and off I'll know what's happened. The rear window looks good.
These windows are the emergency exits and the design is very practical and functional.
I scraped a knuckle this afternoon and the Cadet
has now been blooded. Also, the "55" number refers to the tire pressure!